Are Osama bin Laden and George W Bush related? Yes, if you believe Dr Spencer Wells.

Dr Wells has found new genetic evidence, based on thousands of DNA samples taken across the world over the past 10 years, that shows that all humans alive today have descended from a single man who lived in Africa some 60,000 years ago.

On a recent visit to Madurai and New Delhi to find out more about the origins of Indian ancestors, Dr Wells said he had found genetic evidence to show that Dravidians were the first settlers in India from Africa, and the Aryans followed later.

The experiments of Dr Wells will be telecast on the National Geographic channel on December 15. The programme, 'Journey of Man', tells the epic story of how humans populated Planet Earth. He spoke to Syed Firdaus Ashraf in Mumbai about his experiments in India.

You did your experiments in Madurai. Can you tell us about your findings?

The experiments were regarding the early coastal migration of human beings to Australia. Because, according to our theory, the first time man migrated from Africa was to Australia. India proved a critical turning point for us as genetic testing of isolated Indian populations produces a key genetic marker [one of the genetic changes] linking India as a crossroad for the journey of man to both Australia and Central Asia. So we were looking in the south of India because most Indian scientists said that the oldest population in India stayed in south India. And we found out in our experiments that these people were Dravidians.

Did you do a study of different kinds of species in India, say, for example, of people from the northern side or from eastern and western India also?

We have sampled some other parts of the Indian population. But you know, India is incredibly diverse. And we would love to expand our centre in India. There is a fascinating story to tell about recent migrations throughout the subcontinent. Everybody would be very interested to know about the origins of Bengalis, Maharashtrians and Punjabis.

So you have not done any research in any other part of India?

Unfortunately, most of our samples have been taken in New Delhi and from large cosmopolitan populations because research centres are located in cities. So, it is easy to have research groups. What we need to do in India is to set up a programme to sample different groups.

Some people say Aryans are the original inhabitants of India. What is your view on this theory?

The Aryans came from outside India. We actually have genetic evidence for that. Very clear genetic evidence from a marker that arose on the southern steppes of Russia and the Ukraine around 5,000 to 10,000 years ago. And it subsequently spread to the east and south through Central Asia reaching India. It is on the higher frequency in the Indo-European speakers, the people who claim they are descendants of the Aryans, the Hindi speakers, the Bengalis, the other groups. Then it is at a lower frequency in the Dravidians. But there is clear evidence that there was a heavy migration from the steppes down towards India.

But some people claim that the Aryans were the original inhabitants of India. What do you have to say about this?

I don't agree with them. The Aryans came later, after the Dravidians.

Can you say something about the Indians in the Northeast?

I would love to visit those places. Unfortunately it is difficult for foreigners to visit those areas. I would love to sample them. They look more Asian and the reason for that is there was a massive expansion in East Asia around 8,000 years ago because of the development of rice and agriculture. And these people spread down to the south and to a certain extent to the west in eastern India. So that is why these people look different.

You said that all human beings are related to one man in Africa. Was this the Adam mentioned in the Bible?

It's interesting that both genetic science and the Bible show that there is a single origin of molecule. According to genetic science we come from a single male ancestor. In the Bible too it is mentioned that there is a single male Adam and single female, Eve. Personally, I don't equate that one to one with the story of the Bible because if you come back generations, Adam should have existed in 4004 BC, and our Adam existed 60,000 years ago.

So can you say that you are disputing the claim of the Bible?

I don't like to get involved in religious issues because I am not a specialist in religion. I am a scientist and I demand evidence. And religion is not about evidence but about belief.

How long did it take you to do this research?

Twenty laboratories and about hundred people were involved in this research and it took us ten years to conclude this.

So, how has the scientific community reacted to your findings? Do they agree with your thesis?

They would if they have a careful look. But the problem is that particularly a lot of geneticists do not have archaeological records. So they say that how did these human beings spread out of Africa 60,000 years ago? They say, Oh! That is impossible as humans have been living outside Africa before that but they were not fully modern.

Do you feel archaeologists and geneticists should work together in such experiments?

Absolutely! They must work together, and also cultural anthropologists. It has to be the synthesis of many different fields. Linguists, historians, etc should also come together.

How many people have you used for the experiments?

To create this tape, we probably tried about 50 different populations around the world and nearly 20,000 men. Obviously, that is a tiny subset of the diversity in the world. We have 6,000 languages in the world that equate to the 6,000 populations we should be sampling.

You are very critical of racism.

Yes. We are all much closely related than we ever expected. Racism is not only socially divisive, but also scientifically incorrect. We are all descendants of people who lived in Africa recently. We are all Africans under the skin.